Female Remating in Drosophila ananassae
661
1988). We have conducted experiments on female and male remating fre-
quency by employing several geographical strains of D. ananassae (Singh
and Singh, 1997, 2000; Singh and Singh, 1999). The results have shown that
(a) male remating occurs more frequently than female remating, (b) there
is interstrain variation for remating time for both males and females, and
(c) copulations are shorter in second matings compared to first matings.
D. ananassae females show increases in productivity after remating (Singh
and Singh, 2001). In D. melanogaster, results regarding the effect of density
on female remating frequency obtained by different investigators vary. The
effect of density on female remating frequency in D. ananassae, another cos-
mopolitan and domestic species, has not been tested. D. melanogaster and
D. ananassae are members of the melanogaster species group but belong
to different subgroups and also to different lineages as evidenced by taxo-
nomic and cytogenetic studies (Lemeunier et al., 1986). In view of this, we
conducted experiments to test the effect of density on female remating fre-
quency in D. ananassae by employing 2-h daily observations and continuous
confinement.
METHODS
To test the effect of density on female remating frequency in Drosophila
ananassae, two experimental designs, i.e., (a) a 2-h daily observation design
and (b) a continuous confinement design, were used (Gromko and Gerhart,
1984).
The 2-h Daily Observation Design
In this experiment the following stocks were used: Bhutan (wild
type), DP (wild type) and ca (claret eye color—recessive mutation on
chromosome II). Crosses 1-3 (Table I) were used in this design. In each cross,
virgin females and males were collected and aged for 7 days in food vials.
A single virgin female was placed in a fresh food vial (3-in. length × 1-in.
diameter) with a single virgin male and the pair was observed for 60 min.
When mating occurred, the pair was allowed to complete copulation and the
male was discarded within 1 h of the completion of copulation. Once-mated
females were left overnight in a group of six per vial. The next morning mated
females and fresh virgin males were put into fresh food vials at each of the
four densities. There were 12 vials with 2 pairs per vial, 4 vials with 6 pairs
per vial, 2 vials with 12 pairs per vial, and 1 vial with 24 pairs (see Table II).
No anesthesia was used. All transfers were accomplished by aspiration and
tapping between vials with a funnel. The vials were observed continuously